Centrifugal switch



Patented Apr. 28, 1931 {UNITED STATES PATENT OFFICE wrnnnmm, MOSER, or BERLIN, ennmmr, assronoa T onsnnnscnarr rim mum'- LosE rnnnemmn m. B. 11., or BERLIN, GERMANY, a oonronarron or onnmm GENTBIFUGAL SWITGE Application filed December 15, 1924, Serial No.

My invention relates to s eed governors for electric motors and the e and has for its object to provide a speed governor which will be simple in operation and yet so sensitive and reliable as to be adapted for use in driving radio alternators where great constancy of speed is imperative.

Other objects will be apparent from the following descri tion and claims when considered with t e accompanying drawing wherein:

Fig. 1 is a schematic diagram of my invention;

Figs. 2, 3, 4 are curves explaining the thecry and operation of my invention; and,

Fig. 5 is a schematic diaphragm of a preferred embodiment of my invention utilizing a plurality of contacts.

Referring to Fig. 1 A denotes a rotatable disc which is preferably mounted on some ..horizontal shaft (not shown) driven by the motor whose speed it is desired to govern. Eccentrically mounted on disc A is a weight G secured to one end of spring S. The other end ofspring S is secured to the center of disc A. When the turn plate is rotated, the weight G is subjected to centrifugal force which is resisted by the centripetal force of spring S.

Fixed to weight G is contact point K while fixed to disc S is cooperating contact point 1?. At a certain speed when the force of the spring is substantially equal to the centrifugal force of weight G, an interrupted contact is obtained between contact points K and P due to the action of gravity on weight G aiding and bucking the centrifugal force every revolution. This controls the current flowing thru the contacts K and P which in turn controls the driving motor in any well known way. It is, therefore, seen that the weight G oscillates in a radial direction and within a small range around the desired speed of r0 tation.

755,857, and in Germany December 20, 1923.

If we let w e ual the s eed of rotation on the disc A; c0, t e desire speed of rotation; w, a slightly lower speed than w and an, a\ slightly higher speed than '20,. Then, the device operates as follows:

When an equals w a contact is just made at is smaller than zo and w is smaller than 10,.

Let V equal the time of contact of K and P per revolution of the disc A. V, of course, will range from O to 1, that is, from permanent open to permanent closed in dependence upon the speed of rotation to of the disc A. It will be seen that if V is plotted as a function of w a curve will be obtained from which it may be determined under What conditions the best regulation takes place. Such a curve is shown in Figure 2 and for purposes of this invention will be known as a contact curve. From this curve it is easily ascertainable just what the contact time per revolution is for any given speed. The curve clearly illustrates the following facts:

11 At speeds greater than w, the contact will alrea y be closed.

2. At a speed equal to 'w the time of open contact is equal to the time of closed contact.

3. At speeds less than '20. the contact will already be open.

4. An ideal condition is approached, the smaller the regulating range and the steeper the contact curve at the Working point.

To determine what conditions must exist in order to obtain as near an ideal condition as possible or as feasible the following derivations are necessary.

For any speed a condition of equilibrium exists when the force F of the spring S is equal to the centrifugal force L plus the act1on of gravity on the weight G. Since this ratio of centrifugal mass and force of spring expression must be true irrespective of the is made as small as possible by means of suitangular position of weight G the effect of able construction. In practice this may be gravity must be expressed as G cos where 4 attained by having, for instance, weight G is the angle between the direction of the cenmainly formed by the mass of the spring trifugal force acting on G and the direction of itself. The spring, of course, may be a spiral the force of gravity which is always vertically downward. Thus, the expression becomes:

F=L+G cos (1) Let =a at the moment contact between P and K is first made at some speed w, then Equation (1) becomes:

L=L as w =w Thus,

. 1J=L 'w /w (3) Also let where L is' the centrifugal force exerted by weight G at the moment of contact.

It follows from (3) and (2) that:

FI=L +G cos a (5) from which we have spring or a plate spring which is fastened at one or both ends.

The present invention, furthermore, relates to adjusting the regulating support to a suitable point of the contact curve. It has been found as is evident by the curve in Figure 2 that the steepness of the curve is differout within the range of regulation. Continuing the above mathematical discussion further, it is evident that Equation 7) may be written Since the ratio V=2a/21r, we may substitute V for a in Equation (13).

We then obtain The steepness of this curve is represented by the first derivative of'V with respect to w which is derived as follows:

From differential calculus it is well known that d cosw= (1w dm Therefore from (14) we have:

solving (7 for to we have w.='w /1 G cos a/F (8) let w='w,,, cos a=1 (9) and,

'w='w cos a= 1 (10) substituting (9) and (10) separately in (8) we have w =w /1 -G/F (11) and,

w, =w /1 G/F (12) from which equations it is seen that the smaller G/F the nearer w and ca approach w andconsequently the narrower the range of regulating.

According to the invention, therefore, the

From (7 and from the fact that (cos a+sin a=1) we have:

Equation (15) shows that the steepness of the curve becomes greater the nearer the contact angle a approaches 0 or 180, that IS, if the working point for the regulation is near either 10, or 'w Figure 3 shows a contact curve calculated for F /G=30 and w =3OO0 from which the features pointed out above may be seen.

In accordancewith the invention the speed regulator is so adjusted that the desired speed to which it is desired to maintain the motor lies within the range of regulation near the upper or lower limit of the speed regulator curve. adjusting the regulating current which is read by the instrument I shown in Figures 1 and 5; that is, by noting the variations in current as the contact opens and closes.

This condition can be attained by Small variations, of course, meaning that the device is operating near one of the points mentioned and large variations signify that regulator is operating near the center of the curve.

As a certain finite breadth of regulation is requiredfor the working of the device, w

or tu cannot be approached at will. If par.

ticularly great variations of load or of voltage must be compensated as great a part 0 the range of regulating as possible will be utilized. It will be seen, therefore, that under certain circumstances the steepness of the contact curve will be too small for proper operation. Accordingto this invention this disadvantage is obviated by arranging several equal speed regulators in such a way about the rotating disc that the contacts are closed at equal phase differences between the separate regulators. The contacts in this case are arranged electrically in parallel. Such a device is shown in Figure 5 which shows by way of example only two contacts arranged diametrically opposite to one another. In said figure S, S are the two springs which are attached to the center of disc A on which disc is mounted contact device P, P.

Attached to the free ends of springs S, S are as broad as that. of'a single regulator.

masses-G, G which acts similarly to mass G of Figure 1. Attached to each mass are the cooperating contacts K, K which cooperate with contacts P, P so as to complete the electrical circuit. It is seen from Figure 5 that the radii of the contact masses form equal angles with each other. When the contacts are arranged in parallel as described above and as shown in Figure 5 the contact curve is formed by the sum of the separate contact curves and is, therefore, a much steeper curve than anyone of the separatecurves. At the same time the regulating range becomes n'arrower because V increases more'quickly from zero to 1. This becomes evident upon considering Figure 5 inasmuch as from said figure it may be seen that contact device P, K may be closed when P, K is open, whereas, if only a single contact were present as in Figure 1 the circuit would only be closed when on y that contact was closed, whereas, in Fig ure 5 the circuit may be closed wheneither one of the contacts is closed irrespective of the other.

A contact curve for two speed regulators is illustrated in Figure 4. In said figure a is the original curve similar to the curve in Figure 2 and b the resulting curve when two contacts are used. It is readily seen from Figure 4 that the regulating range is halg I three or more regulators are co-mbinedin the manner as shown in Figure 5 still better results will be obtained since a regulating range is obtained which not only is narrower by three or more times respectively depending upon the number of contacts but even by many more because with an increasing number of regulators only the steeper parts of the original contact curve take part in the generation of the resulting curve. It follows, therefore, from Figure 3 that the breadth of the range of regulating when four regulators are used is reduced to about the 10th part and consequently the steepness of the curve increases to about the 10 fold value.

lVhile I have described only two embodimeans of my invention it will be apparent to one skilled in the art that my invention is not limited to the precise arrangement shown but that many modifications may be made in the circuit arrangements and apparatus without departing from the scope of my invention as set forth in the appended claims.

I claim I 1. In a device for maintaining the speed of a controlled device approximately constant, a rotating disc having its speed of rotation dependent upon the speed of said controlled device, a plurality of centrifugally affected masses, a plurality of resilient means between said masses and the center of said disc, said masses being mounted so that the force of gravity tends to alternately move said masses radially toward and away from the center of said disc, said resilient means and said masses being so proportioned that at the speed desired to be maintained, said masses vibrate periodically and continuously, and means comprising a plurality of contact devices all arranged electrically in parallel and controlled by said vibrating masses for affecting said controlled device.

2. In a regulator including a contact closing device and a circuit adapted to be opened and closed thereby for maintaining the speed of an electrical device approximately constant, a rotating disc having its speed of rotation dependent upon the speed of said electrical device, a plurality of movable make and break contact devices mounted on said disc, and arranged so that the force of gravity acting thereon tends to alternately open and close said contact devices, and the centrifugal force due to the rotation of said contacts with said discs tends to close sa'id contact devices, and means for electrically connecting said contacts in parallel in said circuit, whereby speed of rotation of said device is deterof saidcontacts.

3. In a regulator including a contact closing device and a circuit adapted to be open and closed thereby for maintaining the speed of a controlled electrical device approximately constant, a rotating disc having its speed of; rotation dependent upon the speed'of rotation of said device, a plurality of centrifugally effected make and break contact devices resiliently mounted on said rotating disc and .mined by the ratio of the closed to open time I arranged so that the force of gravity acting I thereon alternately tends to open and close said contact devices and the centrifugal force due to the rotation of said contact devices always tends to perform only one of said operations, said contact devices being so proportioned with relation to the forces acted thereon that at the speed to be maintained the times of open contact and closed contact differ, and means connecting said contacts electrically in paralled with said circuit whereby the speed of rotation of said control device is determined by the ratio of closed to open time of said contacts.

4. In a regulator for maintaining the speed of a controlled electrical device constant, a disc adapted to be rotated in accordance with rotation of said device to be controlled, a plurality of contacts resiliently mounted for radial movement on said disc, all of said contacts tending to close under the centrifugal action set up by the rotation of said disc, at least one of said contacts tending to be opened by the effect of gravity acting thereon and means for connecting said contacts in parallel electrically.

DR. W. MOSER. 

